Complementary metal-oxide-semiconductor (CMOS) image sensors (CIS) are commonly used for sensing images in electronic video and still cameras. For a three-dimensional (3D) CMOS image sensor comprising two stacked wafers, the first wafer may be configured to sense incident light, and the second wafer may be configured to process the electronic signal generated by the first wafer. One challenge of the 3D CMOS image sensor is how to dissipate heat generated within the image sensor because excessive heat may adversely affect the image sensor. For example, malfunction of the image sensor occurs when the operating temperature goes beyond a critical threshold temperature. Another challenge is how to release/discharge the static charge accumulated within or on light shielding metal in the image sensor. The accumulated static charge may cause an electrostatic discharge (ESD), which can damage an integrated circuit (IC) device in the image sensor.
Like reference symbols in the various drawings indicate like elements.